In a pressure regulator, such as the one illustrated in FIG. 1, a piston device can be used for controlling and regulating pressure of an outlet by having one end of the piston device connected with and driven by a valve rod. In the pressure regulator illustrated in FIG. 1, a valve port 300 is arranged between an inlet 100 and an outlet 200, one end of a valve rod 110 is connected with a piston device 120, and the valve rod 110 drives the piston device 120 to move up and down to control the opening and closing of the valve port 300 so as to adjust the pressure of the outlet 200.
Usually, an engineer arranges a perforated baffle plate 130 at the top of the piston device 120, such that a medium coming from the inlet 100 flows into the piston device 120 via the baffle plate 130; thus, the pressure on the upper surface of the baffle plate 130 is equal to the pressure on the lower surface of the baffle plate. Such a design is, however, only based on the hypothesis of a static medium. Once the medium flows, the medium enters a lower part area B of the baffle plate 130 via an upper part area A of the baffle plate 130, and the flow speed of the medium at the upper part area A of the baffle plate 130 is obviously larger than that of the medium at the lower part area B of the baffle plate 130. Therefore, the fluid flow state of the area A is very unstable, such that the baffle plate 130 is subjected to an unstable force, thereby influencing the stability of the supply of the medium at a downstream outlet 200. Furthermore, as a lower cavity of the baffle plate is closed, the flow speed of the medium inside the cavity is very low, and as the speed is inversely proportional to the pressure, i.e., the pressure is small if the speed is high and the pressure is large if the speed is low, the pressure under the baffle plate 130 is larger than the pressure on the upper surface of the baffle plate 130. In turn, the stresses on the upper and lower parts of the piston device are unbalanced, which influences the stability of the supply of the medium downstream as well.